-LRB- CNN -RRB- -- The startling thing , in the long run , is not that the power went out and stayed out in so many parts of the United States during the week just ended .

The startling thing is what we so casually take for granted :

Flip a switch , and the lights in your home instantly blaze to life .

Turn a knob , and clean water comes rushing into your sink or bathtub .

Pick up a telephone , and you 're talking with someone halfway across the country or halfway around the world .

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Right now , the most pressing matter is to get the electricity back on in the places that are still without it . People are in despair ; people have died . Fierce storms , along with near-record-high temperatures , combined during the final days of June and the first week of July to bring down multiple power systems and leave millions of people sweltering in the dark .

But once all is up and running again , it might be good to pause and think about how fragile all of our assumptions are .

For much of the time that the continental United States has been a part of the planet , few of the life-easing developments we nonchalantly take on faith seemed remotely possible .

Electricity ? Running water ? Air conditioning ?

They were the stuff of science-fiction novels . Ours was a land mass of forests and rivers and deserts and plains , a tangled and disconnected tableau that disappeared from view with the blackness of night .

We -- not you and I , but our ancestors -- figured out how to change all that . By the time recent generations came along , everything seemed so endlessly convenient . The battle for civilization had been won .

Which is why a week like the one just past is such a sobering reminder that we are always just an unanticipated disaster away from a trip into the primitive America that existed before .

Doubt it ? Ask your fellow citizens who waited and waited for someone to turn their lights back on last week .

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In the blast-oven heat that stifled much of the nation in recent days , the absence of air conditioning felt anguishing . But that situation was , for most of America 's history , so commonplace as to be unremarkable . Summers were for sweating , and for drawing the blinds , and for sleeping on porches . It was n't until the 1920s that movie theaters featured early versions of air conditioners , which proved to be an enormous draw for the public who yearned to escape their broiling homes . Department stores in the 1930s lured customers by offering them a chilled-air respite from the scorching hours they spent in their houses .

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According to the Carrier Corp. , the pioneering air-conditioning manufacturer , as late as 1960 few college buildings featured air conditioning , and virtually no elementary or high schools had it . Private residences ? For the most part , they were the last to convert . Window units were available , but by 1965 , according to Carrier , only one out of 10 U.S. homes had central air .

But when our daily lives change for the better , human nature lulls us into all but forgetting what preceded . We do n't even question the marvelous advances that once seemed out of reach .

One of the funniest -- yet most perceptive and provocative -- news-conference questions I 've ever been aware of was asked in the 1970s by Ron Powers , who was then the brilliant young television critic of the Chicago Sun-Times .

If memory serves , the event was some sort of press gathering organized by CBS to discuss the network 's upcoming schedule . After the preliminary announcements , the floor was opened for questions . Many of the reporters in attendance asked about the stars of the new shows , and about ratings trends , and about programming decisions .

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Then Powers raised his hand , and asked :

`` How do you make the pictures go through the air ? ''

As delightful as his telling of the story was back then , I thought of it again last week , in a much more serious context . How do the essential things in which we place our confidence really get done ? And are we right to think we can forever count on them ?

The uneasiness and fear when the power went out last week extended beyond the nuts and bolts of engineering ; instead , it was almost primal .

It was a reminder of the unthinkable , of scenarios as potentially nightmarish as a sneak attack by foreign enemies .

It was an unwelcome premonition of things we do n't even want to consider :

We flick the light switch , and nothing happens .

We twist the knob on the faucet , and nothing emerges .

We punch a number into the telephone , and hear only silence .

We turn on our computers , and are greeted by blankness .

And then , darkness falls .

The opinions expressed in this commentary are solely those of Bob Greene .

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Bob Greene : Parts of U.S. lost power ; we should reflect on how we take comfort for granted

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He says not long ago , no one had electricity , running water ; people changed that , mostly

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He says we are always one unanticipated disaster away from a trip into primitive America